Add section_type to vacuum_clean_zone_predefined config section.

[khenderick]

See my (editted) comment #724 (comment) (in the wrong topic) referring #662 (comment).

This PR adds the missing section_type to the docs.

[jgkawell]

Would be great if this were merged. I spent far too long trying to figure out why my setup wasn't working and this was the issue.

[sca075]

Would be great if this were merged. I spent far too long trying to figure out why my setup wasn't working and this was the issue.

I'm adding the service calls in my project and I catch it correctly is there any way to have predefined zones with the "original" Valetudo? If not properly I can try to figure out how to.. somehow do it.. Rand256 as you guys can see later on is supporting those by default. Of course the card could help here too.